It is known that a conventional voltage regulator module (VRM) can be used to regulate a DC voltage supplied to a load such as a microprocessor. A VRM can include a power converter, such as a DC-DC converter, and may include other components such as a controller for controlling operation of the power converter.
An example of a DC-DC converter is a synchronous buck converter, which has minimal components, and therefore is widely used in VRM applications. In an example application, the input voltage to the buck converter is typically 12VDC. An output voltage produced by the VRM may be 5.0VDC, 3.3 VDC, or even lower.
Conventional multiphase interleaved VRM power supply topologies can include two or more power converter phases that operate in parallel with each other to convert power and supply power to a corresponding load. Implementation of a multiphase voltage converter topology (as compared to a single voltage converter phase topology) can therefore enhance the output current capability of a power supply system.
A typical configuration of a VRM such as a so-called synchronous buck converter includes an inductor, a high side switch, and a low side switch. A controller associated with the buck converter repeatedly pulses the high side switch ON to convey power from a power source through the inductor to a dynamic load. The controller repeatedly pulses the low side switch ON to provide a low impedance path from a node of the inductor to ground in order to control an output of the buck converter. Thus, the energy stored in the inductor increases during a time when the high side switch is ON and decreases during a time when the low side switch is ON. During switching operation, the inductor transfers energy from the input to the output of the converter to keep the output voltage at a relatively fixed value.
There has been increased motivation in the industry to produce yet more efficient power supply circuits so as to reduce losses. Accordingly, a significant amount of money has been spent to develop more efficient power supply circuits.
In addition to producing higher efficiency circuits, there has been an impetus in the industry to supply health/status information associated with operation of a power supply circuit to other entities via a respective communication link. One such parameter is the efficiency of a respective power supply circuit. However, this parameter is not easy to measure or calculate because it is based on input current or input power, which itself is difficult to measure.
In general, the efficiency of a power supply circuit can be calculated based on the amount of power supplied as an input to the power supply circuit versus the amount of power outputted by the power supply circuit to power a load. When there are very few losses in a power supply, the efficiency is very high because most input power is conveyed to a load.
One way to measure input current of a power supply circuit is to measure a voltage across a resistor disposed in series with an input voltage source used to power a power supply circuit. Based on the voltage across the series resistor, it is possible to detect the amount of current supplied by the voltage source the power supply circuit. Input power can be calculated based on the detected amount of input current at a particular input voltage.